Method and means for direction finding



June 9, 1936. A. LEIB 2,043,624

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1952 sSheets-Sheet 1 m y i /60" A 0' MOMW 3 90 270 0 yaa" INVENTOR AUGUST LEIBATTORNEY June 9, 1936. A. LEIB 2,043,624

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1952 ssheets-sheet 2 INVENTOR AUGUST LEIB 2 BY V rv ATTORNEY 9, 1936. 5 LElB2,043,624-

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1932 3Sheets-Sheet 3 k [M g A]! 2 U? l i I Full" INVENTOR AUGUST LEIB ATTORNEYPatented June 9, 1936 KJNE'EED STATES PATENT OFFICE METHOD AND MEANS FORDIRECTION FINDING Application January 27, 1932, Serial No. 589,100 InGermany June 15, 1926 7 Claims. (Cl. 250-11) The present invention,which is a continuation in part of United States application #198,926,filed June 15, 1927, relates to an arrangement for directionalsignalling and in particular for direction finding work in wirelesstelegraphy. This invention is universally useful, but is illustrated asbeing particularly for use on vessels, automobiles, ships, or aircraft.

It is well known that for direction finding work loop or coil antennae,or other antennae having directional characteristics, are employed, andthat the intensity of the signal currents set up in the aerial system byabsorbed signal energy vary in accordance with the particular positionof such directional. antenna relative to the position of the source ofsignals. In using such devices, it has been found that an absolute zero,that is, a complete absence of current, in the absorption circuits cannot be obtained no matter how the directional antenna is positioned withrespect to the distant transmitter. Such lack of sharpness of minimumresponse of the absorption structure to incoming current intensity maybe the result of various causes. These causes may reside either in thedirectional absorption structures themselves or else in efiects externalto the latter. Particularly on ships there is one special source ofdisturbance, namely reradiations from adjacent metallic structures orwires or other conducting elements or structures mounted on the ships.This re-radiation from adjacent conducting elements to the directionalaerial system results in the introduction in the circuits of currentsnot in phase with the current therein representative of directlyabsorbed signal energy. These disturbing currents result in masking thenull point on the energy curve representative of the absorptioncharacteristics of the receiver and result in a reading which does notgive the true direction of the source of signals. This re-radiatedenergy may be of any frequency, and may be of a frequency above or belowthe signal frequency but is in general in its worst form thought to beof a frequency higher than the signal frequency. This effect ofre-radiation of energy from adjacent conducting elements to thedirectional absorption system is known as mast effect. It must be keptin mind that the result of this out-of-phase energy in the loop circuitis to dull or mask the null point of the loops signal absorptioncharacteristic rather than to shift it, and the object of the presentinvention is to provide means to clear up or make more definite the nullpoint of the characteristic curve rather than to shift it.

Briefly and broadly the above difficulties are obviated in accordancewith the present invention by introducing into the loop circuit energyto oppose and compensate the energy induced therein from the adjacentmasts or other conducting elements.

More in detail, the null point of the characteristic curve of theabsorption system is made more sharp (i. e., energy reaches zero) by theintroduction into the absorption circuit or circuits associatedtherewith of energy opposite in phase and equal in amplitude to thedisturbing energy. This may be accomplished in any manner. Applicantuses a vertical aerial coupled to the loop circuit to introduce thecompensating energy. It will be understood however, that directional ornon-directional auxiliary antennae may be used which occasion anadditional action on the receiving apparatus so that the disturbingactions are compensated and the null point rendered more definite.

One form of the invention is shown in the accompanying drawings inwhich:

Figure 1 shows diagrammatically the circuit arrangement of a loop andcompensating antenna arrangement and their connection with a receiver;

Figures 2 and 2a show, for purposes of illustration, the directionfinder of Figure 1 as installed on a ship;

Figure 2b shows in detail a modification of a part of the device ofFigures 2 and 2a;

Figure 3 is a curve showing the relation between loop positions andabsorption characteristics of the loop;

Figure 4 shows the relative positions between the antennae and aninductance associated therewith; while,

Figures 5 and 6 illustrate modifications of the arrangements of Figures1 and 2.

Referring to the drawings, and more in particular to Figures 1, 2 and 2athereof, the loop antenna R comprises symmetrical energy absorptionportions r1, r2 closed through inductances m1, m2 and a couplinginductance 1'. For reasons which will appear more in detail hereinafter,these coils may be symmetrical and equal or unsymmetrical and unequal.The loop aerial inductance may be tuned to the signal frequency by acapacity K connected across the terminals i, 3 thereof. Compensatingenergy is obtained from a vertical aerial A connected through a tuningcapacity TC and coupling inductance a to ground G or equivalentoountercapacity. The amount of the inductance in this vertical aerialmay be regulated by moving the points 8 and 9 along the inductance a.The'inductance a is coupled as shown to the inductance r. The saidauxiliary antenna A serves to introduce an additional signal potentialin the loop antenna circuit. 'The variable capacity TC, and inductance ainsures that said energy may be maintained in the proper phase andamplitude to suppress and action from the auxiliary antenna will varybetween z ero,'in-ship position I relative to the sigcompensate currentstherein due to re-radia'tion from adjacent structures; 'ThelOOIIV'R hasone terminal connected through a connector 3 to the grid of an electrontube e, the filament of which is connected by connector 1' tothemidpoint of inductance r. The other terminalof loop R. is connectedby lead 4 through a variable capacity no to the anode of thermionic tubee. The voltage set-up across the portion 12, the conductor 2,

m2, lead 6 and half of the inductance rbythe signal is impressed acrossthe cathode control electrode impedance of e. Anode grid reactance -iscontrolled by the condenser connected between the anode andthe-inductance m.

Now, the influence of -re-radiation of signal energy upon theloopantenna circuit differs according to the particular position of thevessel relative to the source of signalv energy so that the requisiteauxiliary antenna; effect required for the compensation of thedisturbing action must be varied according to the position of theship,-with the result that the coupling between the auxiliary antenna Aand the loop antenna or the receiving apparatus must be varied accordingto the position of the ship at any given time. To make such alterationsis a rather complicated task under practical conditions of working,since in case of improper or unskilled operation and manipulation of theapparatus the compensating energy will be introduced in the wrong phaseand amplitude. This will cause deviations from the true bearing'of thesignalling source. Even in case a skilled direction finderoperator is incharge the changing of the-coupling relations j between A and R.involves a' by no means inconsiderable loss of time.

Now, according to the present invention, this inconvenienceisobviated'thus: 'The auxiliary antenna A is coupled to the receivingantenna R.

through a 'coupling'impedance ha'vinga variable adjustment which isautomatically controlled in accordance with themovementoffthe loopaerial.

It has been found'that the disturbance due to re-radiation changeswiththe change of position of the vessel in accordance with a simpleperiodical 'law. "The manner in which thedisturbing efiect varies withrotation of the loop or .turningof the ship whilethe'ioopis pointedtoward a source may be seen by an inspectionof Figure 2a in which twopositions, .I .and 2,1'of theship are indicated. from these figures itwill be seen that in one case the. disturbance effect on the loop is ofa maximum amount, while. inthe other case no disturbance at all ispresent. Suppose the transmitter is'located in the, direction indicatedby the arrowS. Suppose r represents the position of the receivingantenna .e. .g. the position of R of B represents a re-radiating mast orother conductor, whose ,re-radiation efiect, in

this position, acts in the same direction as the Wave coming in from thedistant transmitter. In this particular position of the receiving loopR, no additional action from the auxiliary antenna A is required becausethe loop R has its plane at right angles to the wave from the source andthe re-radiating memberB. "But the situation is different when theship'is in the position a sinuous curve, as=shown in Figure 3. *cordancewith the present invention this varymarked 2. In this case, theexcitation of the loop by the waves transmitted from B will be of amaximum amount since the plane of the loop R points toward there-radiating member B. Hence, an equally large opposite action from theauxiliary antenna A of Figures 1 and 2 will be required to introducecompensating energy into the loop circuit. Hence, it will be seen thatthe naling source, and a maximum, in ship position 2, or between thevalues present when just the opposite positions are dealt with.Consequently, the variation in disturbing effect from a re-radiatingmember. onA during a total turn of the vessel about 360 degrees can berepresented by In acing efiect of the re-radiation on the loop iscompensated by an opposing efiect which is introduced-fromA tothe loopcircuit in amounts which vary directly with the variations inreradiation. In the embodiment shown thisis accomplished by varying thecoupling between the auxiliary antenna and the receiving apparatus orframeaerial in the same manner as the intensity of the re-radiationvaries. This --is accomplished by arranging "the coupling coi1s-so "thatone thereof is rotatable with the loop, while the otherone-is'mountedstationary-on the ship -so that ithas no movement relative to B. Theposition of one of the coils (that is, the one-turning with the loop)remains unvaried-with respect to the loop, while its disposition-withreference to the re-radiating mast will be varied'as the loop isrotated. The second coil, however, is so disposed that its positionwith'reference to the =re-radiating mast remains unchanged, while its-position with reference to the distance trans- ;mitter is varied. Inthe specific embodiment shown the coil' a is fixed relative to the shipwhile the coil 1" is movable with the loopR.

The manner-inwhich the loop, the balancing coils and the couplinginductances may be 'mounted on the ship willbe' understood byr'efer ringto 'Figure 2 of the drawings. In Figure 2 the coil 1 representative'ofthe loop position is "fixed in the 'plane of 'the-loopR, while the coila representative of 'theve'rtical aerial efiect coupling is fixed to theship. The coilr is mounted on a sleeve p'clamped at q to the shaftcwhich supports the loop-R. The loop-R and coil 1' may be rotated bymeans of hand wheel I) fastened to shaftc. The vertical aerial couplingcoila is stationarily'secured, asindicated by members g to support (1which'may in turn be fastened to the ship. "The coil 11 is stationarywith respect to r, c, and-R. The direction finder scale 1 is fastened-tod and cooperates with a; pointer secured-to d to indicate the, pointingposition of the'loop R. It'will be seen that as the loop is rotatedfthecoupling between r and a-will vary fromminimum, as indicated, inposition I of 2a,

where no compensating energy is induced in the loop or receiver circuit,to maximum coupling at whichamaximum amount of energy is induced from-ato thereceiver circuit or the loop. ,The latter position is indicated inposition 2'of 2a..

For convenience of illustration the coils are shown in position ofmaximum coupling in Figure 2.

The mutual position of coils r and a, in case of turning of the ship;can be seen from Fig. 4,

' where four positions are indicated corresponding to the turning "of'the'vessel, through zero, 90, 1

180, and 2'70 degrees. The case here cited is particularly simplebecause the assumption has been made that both the transmitter as wellas the disturbing source and the loop antenna are located upon astraight line. Whenever this condition is not fulfilled, the zero pointof the correction curve will shift, and then a coupling would have toexist also in position I, in other words, the position of the twocoupler coils with reference to each other must be turned a certainangle.

In actual practice it may be found that in addition to the re-radiatingstructure B considered above, compensated as indicated above, there maybe other re-radiating structures which may very well cause a constantdisturbance independent of the turning movements of the ship. Thepresent invention obviates thisby the use of a fixed coupling betweenthe auxiliary antenna circuits and the receiving circuits or loopcircuit in addition to the variable coupling described above. The fixedcoupling compensates the constant source of disturbance. In the presentinvention this fixed coupling is obtained by means of coils m1 and mz inseries with the loop circuit, as indicated in Figures 1 and 2. m1 iscarried on a support hr fastened at 1'1. This coil may be adjusted tothe desired position with respect to a and fixed in said position bymeans of said screw i1. m2 which is also in series with loop R, ismounted adjacent a on a support hz. m2 is movable with respect to a asindicated. The position of me with respect to a is indicated by pointeri2 cooperating with a scale 1'. The position of 1m may be varied byhandle iz.

If the disturbing actions bear a more complicated relationship to theposition or turning of the vessel, compensating of the disturbingactions can be insured by altering the mutual positions of the couplingcoils according to a law different than the one hereinbefore described,that is to say, in a way other than according to a sine law. This couldbe accomplished, for example, by the aid of a cam, as illustrated inFigure 2b.

The non-sinuous or irregular movement of the coupling coil 1' withrespect to the coil a. may be accomplished by fixing a cam ID to thesleeve p bolted at q to the shaft e so that said cam rotates with saidshaft when the loop R is rotated. The surface of the cam IU of varyingradius acts through roller I2 on a lever l3 which oscillates a rack l5about a point 14. The rack I5 cooperates with a pinion 16 torotate shaftI1 to which pinion I6 is fixed. The coupling coil 1' is fixed to shaft[1 for rotation therewith. The roller [2 is maintained in contact withthe periphery of cam l by spring l8 fixed at I9. The center of cam It!may be given any shape, and is given a shape such that the couplingbetween a. and 1' is varied directly as the intensity of the re-radiatedenergy from the one or more adjacent structures varies.

In order to realize variation of the potentials induced by the auxiliaryantenna in relation to the potentials of the loop circuit, anotherscheme would be to vary the electrical resistance of one or bothantennae in dependence upon the turn of the vessel, instead of byvariation of the coupling between the antennae and the receivingapparatus.

An understanding of the last mentioned modification will be had byreferring to Figures and 6 of the drawings. The arrangement shown inFigures 5 and 6 is quite similar to the arrangements shown in Figures 1and 2. In Figure 5, however, the coupling inductances m1, 1112 areomitted and the terminals of a are connected through leads I and 2 tothe loop R. Here the center'point of a is grounded, and the signalvoltage across T2 is impressed between the grid and cathode of tube R asin Figures 1 and 2. The potential introduced from the vertical aerial Athrough coupling coil a to the loop or receiver circuit may bedetermined by adjusting point 20 along a resistance W in series with a.The manner in which the position of 2!) along W is determined by theposition of the loop is illustrated in Figure 6. In Figure 5 the sleevecarries a pinion 2| cooperating with a second pinion 22 which drives thecontact member connected to A and bearing on resistance W. When theshaft 0 is rotated to rotate the loop, the pointer 20 is rotated,thereby varying the amount of resistance in the vertical aerial circuitand consequently determining the amplitude ofthe vertical aerialcomponent introduced in the loop through coupling a, r. The resistanceturns of the rheostat W may be disposed on their support in non-uniformmanner corresponding to the regularity or irregularity of the desiredcompensating action.

The potentials induced from the auxiliary antenna, as is well known, maybe brought to act directly upon the loop circuit as shown, or else uponintermediate circuits or upon direct reception indicators. These aredifferent well-known schemes of combination of the effects of twoantennae.

In all of the above arrangements the output elements of tube e may beconnected with an indicating means directly, or by way of amplifiers,rectifiers, etc. The tube e may therefore be a detector or a radiofrequency amplifier. ure 1 the anode electrodes of e are connected withan indicator T. -In Figure 2 the output electrode of tube e is connectedthrough a capacity 24 and high resistance 25 to the input electrodes ofa second tube 6' which may have an indicator in the output thereof asshown or be connected with further thermionic tubes. In Figure 5 theoutput elements of tube e are connected with an indicator while inFigure 6 they are connected with a relay 28 which in turn is connectedwith an indicator T.

Having described my invention, it is understood that I do not limitmyself to the form shown, but what I claim is:

1. A directional receiver to be used adjacent metallic structures whichtend to re-radiate signal energy comprising, a frame aerial circuitincluding a plurality of series inductances, the first of whichinductances is rotatable and is exposed to the direct field of thesignal energy, the second of said inductances being also rotatable withsaid first named inductance, a third one of said inductances beingstationary with respect to said rotatable inductances, and a verticalaerial circuit including an inductance coupled to said second and thirdinductances.

2. A directional aerial system as specified in claim 1 in which cammeans is provided for controlling the coupling between said inductances.

3. A receiving system for accurately determining the line of directionand sense of direction of a signaling source including, a frame aerial,said frame aerial including a pair of rotatable inductances exposed tothe signaling wave, said inductances being in series with a plurality ofcoupling inductances, a pair of which is fixed and another of which ismovable, a circuit for symmetrically grounding said loop aerial, avertical aerial comprising a linear conductor and tuning means, acoupling inductance connecting In Figsaid: vertical aerial toraground,said, couphnainzi dnctance being coupled to said Lmovable,inductanceinsaidfrarne aerial circuit, means for simultaneously rotatingsaid first named pair. of inductances in said frame 1 aerialiand' saidmovable inductanca and a thermionic translating device havingits controlgrid connected toa point :on saidframe aerialicircuit and .its cathodeconnected to ground. e

4:. In a radio direction finding system, a pair of rotatableabsorptionmembers each including a plurality of turns .ofconductingmaterial, a plurality of iinductances in series. connectingsaid absorption members inseriesto form therewith a directional antennacircuit, a connection between the electrical midpoint of the said an-=tennacircuit. and groundga'vertic'al aerial path,

an inductance in said vertical aerial. path, an adjustablecoupling-between said lastnained ;in-;

ductance and one of said first named in'ductances, and a variablecoupling between said inductance in said vertical aerial path andoneof'said first 2 named inductances, and cam controlled means operable:in accordance with theorientation of said-frotatable absorption membersfor adjusting the last said coupling; 1 I I I I 5; Adirectional antennasystem comprising two rotatable inductive absorption memberaa firstinductance mounted: for rotation with. said two absorption members,similar series inductances connecting the opposite ends of said-first:inductance to adjacentends of said absorption members, a condenserconnecting the remote terminals said tuned I closed circuit to bebalanced with respect. to ground.

Itr az'directional,antenna-system,.a first pair of. similarsinductancesadapted to be exposed to radiant energy, a secondpair of similarinductances; leads connecting. said second pair of similarinductances inseriesbetweenterminals of said: first pair of inductances, an oddinductance -symmetrically disposed in circuit between thetwozinductances of thesecondpair, a tuning a capacity connected in shuntwith all of said inductances to; form therewith a tunable circuit,

and: a connectionbetweena movable point on said thirdinductance'andground to permit said tunable circuit to be balanced with respect toground.

"I; In :a devicerfor-receiving radiant energy and forproducingcurrentscharacteristic of the direction and sense of direction of thesourceofsaid energy, a'loop aerial having 'twoportions each including aplurality of turns of conductive material exposed tothe radiant energy,an inductive circuit comDrising-aplurality of portions in series andhaving'a. series connection between the two portions ofssaiddoopaerial,a connection between a point of electrical symmetryon saidinductivecircuit andxground, meansincludinga tuning capacitor interconnecting thefree ends of the turns of each aerial portion for establishing aclosedcircuit which may be tuned to the frequency-cithe radiant energyto. be received, a

vertical antenna, an inductance connected theree to and to earth'whichinductance, is coupled to the first said inductivexcircuit and anelectron discharge device having. an anode, a cathode and a controlgrid,said controlgridand said anode beingrespectively, coupled toopposite free ends of said. aerial portions and said cathode beinggrounded; said electron discharge device having a ivorkcircuit connectedthereto for'indicating the eifects ofthe received radiant energy.

AUGUST LEIB.

